1. Field of the Invention
This invention relates to a cigarette mouthpiece which can be attached to a cigarette in combination with a filter.
More particularly, it relates to a cigarette mouthpiece wherein the smoke passage inside of a tubular exterior cylinder has the form of a helix so that the smoke passing through said passage flows through a helical path about the central longitudinal axis of the exterior cylinder. The fine particles of condensable components in the smoke are thereby efficiently separated from the gaseous components, while the collision and adhesion of said particles to the passage wall are effectively enhanced.
2. Description of the Prior Art
A conventional filter for cigarettes contains filter medium of fibrous material which is wrapped with an external paper layer to form a filter tip and the filter tip is attached to the cigarette. The fiber initially employed for cigarette filters was cotton and later a filter tip comprised of acetate tow was used.
The essential functional requirement of cigarette filters is that they should remove the smoke components considered by smokers as being undesirable for reasons of aroma, taste and/or health. Therefore, a great many cigarette filter devices has been proposed for achieving the proper balance between the suction resistance or the pressure drop in the passage of cigarette smoke components through the filter and the amount of unwanted smoke components removed by the filter.
Different types of filter materials are currently available which are designed to enhance the adsorption efficiency principally. These include non-acetate fibers such as rayon and paper, combinations of different types of fibers such as acetate-paper mixtures, or combinations containing activated charcoal.
Furthermore various types of filter tips are available, for example, a device for introducing ambient air into the upstream side of the filter tip thus lowering the temperature of the smoke components reaching the mouth of the smoker and retarding the combustion of the cigarette tobacco, and/or a plastic mouthpiece for enhancing the self-supporting effect of the filter tip and having dimensions and shape providing a pleasing feel on the smoker's lips and also a mouthpiece having a baffle or the like for separating the condensable components which form as the smoke cools during its passage from the combustion zone to the mouthpiece so as to deposit said condensed components on the inner surface of the mouthpiece, thereby improving the absorption coefficient (removal of condensed components) to some extent.
One example of a known cigarette mouthpiece of this type comprises a mouthpiece (hereinafter referred to as "straight type") wherein an axially extending straight wall or partition is provided inside a thin exterior tube, thereby dividing the interior of said tube into at least two parallel smoke passages. Another known mouthpiece (hereinafter referred to as "baffle type" as shown in FIGS. 1 and 2) has axially spaced walls inside the tube and extending perpendicular to the axis thereof. These walls are provided with transversely offset through holes so that said walls serve as baffles and the smoke flows through a zig-zag path.
Although a mouthpiece of the "straight type" has only a small pressure drop during smoking, it also has only a minor effect of separating and depositing smoke components on the surfaces of mouthpiece so that this type of mouthpiece provides primarily only an improved feel in the mouth of the smoker. On the other hand, a mouthpiece of the "baffle type" has an effect of separating condensible smoke components, but because of the complicated shape of its smoke passage, the pressure drop thereacross is relatively high so that a stronger suction must be applied by the smoker. For example, when smoke is drawn through the exterior cylinder 1 in the direction A as shown in FIG. 1, the stream undergoes a total pressure drop several times as large as the drop that occurs when only one wall is present. The total pressure drop comprises an iris loss at the entrance position 4 between two adjacent partition walls 2, a divergence loss at the outlet position 5, and a pressure loss due to the change of direction between said outlet position 5 and the subsequent entrance position 6. Therefore the advantages and disadvantages of this "baffle type" mouthpiece are contrary to those of the "straight type" mouthpiece.